10 signs you need a rest day: #runningtips

After disappointing performances in a couple of key tune-up races last fall, a depleted Ryan Hall made the hard decision to withdraw from the Chicago Marathon . Too many grinding 15-mile tempo runs at a five-minute-per-mile pace at 7,000 feet with too little rest afterward had finally caught up with him. "I love to push my body," he says. "Recovery is the hardest part of training for me." Problem is, if you don't take time for proper R&R, your body won't adapt to the stress of your training—you won't get stronger or faster, explains Stacy Sims, Ph.D., at the Stanford Prevention-Research Center, School of Medicine. Neglect recovery for too long, and you will start to lose strength and speed. You'll sink into the black hole known as overtraining. First, your sleep patterns and energy levels will feel the effects. Eventually, your immune system crashes, and you lose your appe...